Combustor assemblies are integral components of gas turbine engines. The combustor assembly is positioned in flow communication with a compressor, a fuel injector and one or more turbines. During engine operation, pressurized air from the compressor and fuel from the fuel injector enter the combustor. The resulting fuel/air mixture is ignited to produce a high temperature combustion gas stream. The hot combustion gas then flows downstream to turbines for energy extraction.
As the cost of natural gas and the adverse effects of its emissions increase, there has been a trend to use hydrogen as a fuel in stationary gas turbine engines. The flame speed and flashback tendency of hydrogen are much higher than natural gas fuels, requiring significant changes to the gas turbine combustors. There are two well-known methods to reduce flashback: 1) dilute the fuel/air mixture with gases that do not burn, such as nitrogen or steam; or 2) increase the inlet velocity of the fuel/air mixture above the flame propagation speed. Both of these methods reduce the overall turbine efficiency and have practical limitations.
An example of a gas turbine that reduces undesirable nitrogen oxides (NOx) and carbon monoxide (CO) emissions by providing a more homogeneous fuel/air mixture for main stage combustion is disclosed in U.S. Pat. No. 6,082,111, entitled ANNULAR PREMIX SECTION FOR DRY LOW-NOx COMBUSTORS. However, the combustors disclosed in that patent will not allow the use of fuels such as hydrogen due to the flashback problem alluded to hereinabove. Flashback occurs when the flame speed of the fuel used is excessive and a flame literally flashes back to the source. This will occur when hydrogen, for example, is used in the conventional nozzle type combustors such as those disclosed in the above-cited patent.
Another example of a combustor is disclosed in a technical paper entitled CONCEPT AND COMBUSTION CHARACTERISTICS OF ULTRA-MICRO COMBUSTORS WITH PREMIXED FLAME, by S. Yuasa, et al, and published in the proceedings of the Combustion Institute 30 (2005) 2455-2462. The micro-combustor disclosed in that paper is designed for use in ultra-micro gas turbines as an application of power micro-electromechanical systems (MEMS) technology. Such micro-combustors are low power laminar flow devices operating at low pressures and low temperatures, and as a result, heat loss and flame stability are significant considerations in the combustor design while flashback is of little concern.